1. Field of the Invention
The present invention relates to a calibration system and calibration method calibrating mechanical parameters.
2. Description of the Related Art
In industrial robots, programming using teaching playback is being widely used. According to this method, a robot repeatedly moves to teaching positions taught by the program.
A robot controller utilizes a mechanical model mathematically representing a robot to perform numerical calculations and convert teaching positions of a program to command positions in a coordinate system of the robot. A mechanical model generally includes some error with respect to the actual mechanism of the robot. The position which the hand of the robot reaches will not perfectly match the command position. That is, if the error between the actual position reached by the hand and the command position is small, the positioning precision becomes higher.
The parameters included in a mechanical model (below, sometimes referred to as “mechanical parameters”) include processing error or assembly error of the component parts of the robot and are unique values differing with each robot. Therefore, when the component parts of a robot are changed, unless adjusting the mechanical parameters, the positioning precision of the robot is liable to fall.
If marking component parts before replacing a motor, the method of adjusting the positions of the component parts so that the marks match after replacing the motor (below, sometimes referred to as the “mark reference method”) is known.
Further, Japanese Patent. Publication No, 54-162565A discloses the method of forming a relief shape at the body of the robot and using a measuring apparatus to detect the position of the relief shape so as to determine an origin of an axis. Japanese Patent Publication. No. 1-087182A discloses the method of utilizing a light receiving device attached to the robot and a laser emitting part to calibrate an origin.
Japanese Patent Publication No. 2001-018182A discloses a method of measuring a 3D position of a front end position of a robot after change of posture of the robot to thereby calibrate the mechanical parameters. Japanese Patent Publication No. 2001-105357A discloses a method of utilizing the fact that a length of a wire attached to a hand of a robot changes along with a posture of the robot so as to calibrate the mechanical parameters. Japanese Patent Publication No. 2008-012604A discloses a method of making a robot move in accordance with a position of a target after change of the posture of the robot and a distance between a light receiving device and the target and calibrating the mechanical parameters from the results.